HR: 0800h
AN: OS11B-0505    [Abstracts]
TI: Living coccolithophores from the Bay of Bengal (NE Indian Ocean)
AU: Mergulhao, L
EM: mlina@rediffmail.com
AF: NationalInstitute of Oceanography, Dona Paula, Dona Paula, Goa 403004, India
AU: * Guptha, M S
EM: medimi@rediffmail.com
AF: NationalInstitute of Oceanography, Dona Paula, Dona Paula, Goa 403004, India
AB: Sediment traps collected from three mooring sites located longitudinally at northern (NBBT), central (CBBT) and southern (SBBT) Bay of Bengal were analyzed for coccolithophores. It yielded twenty five species of coccolithophores represented both by coccospheres and disintegrated individual coccoliths. Coccolithophore fluxes showed that the highest fluxes occurred at CBBT with an average flux of 114.68 x105 m-2 d-1 followed by SBBT and NBBT with the average values of 109.35 x105 m-2 d-1 and 41.55 x105 m-2 d-1 respectively in the shallow traps. Similarly, except for a significant increase in F.profunda at SBBT and CBBT and its decrease at NBBT, the remaining species continued to display similar trend in the deep traps (2146-3011m depths) also. It was also observed that Gephyrocapsa oceanica, was the most abundant species followed by Umbilicosphaera sibogae, Umbellosphaera irregularis, Florisphaera profunda, Emiliania huxleyi, Calcidiscus leptopora and Olithotus antillarum in the shallow traps (1156 to 2558m depths). Overall fluxes of coccolithophores observed in the Bay of Bengal were comparatively lower than those reported from the Arabian Sea. Besides, temporal distribution clearly displays distinct seasonality. Total fluxes increased with depth from shallow to deep traps due to lateral advection, which was very conspicuous at SBBT. In general species such as G. oceanica, U. sibogae¬ and E. huxleyi were dominant displaying a distinct seasonality with peak fluxes associated with SW and NE monsoons, reflecting their affinity to nutrient rich waters accomplished by river plumes, upwelling and advection at NBBT, CBBT and SBBT respectively. While U. irregularis, an indicator of oligotrophic conditions recorded peak fluxes only during spring intermonsoon period at all the three trap locations demonstrated its preference for nutrient depleted waters caused by increased sea surface temperatures, stratification and lack of supply of nutrients. F. profunda a deep dwelling species recorded its peak fluxes during fall intermonsoon (Oct/Nov) in the northern and the southern traps and during spring intermonsoon (Apr/May) in the central and the southern trap indicating the presence of a deep nutricline. Interestingly, coccoliths affected by very conspicuous dissolution and mechanical break down were encountered at all the three moorings most part of the year. This may by attributed to intense biological activity.
DE: 1616 Climate variability (1635, 3305, 3309, 4215, 4513)
SC: Ocean Sciences [OS]
MN: 2007 Fall Meeting